Significant energy is required to heat and cool buildings occupied by humans. Subject to the seasons and the weather, buildings located in the south require significant energy to effect cooling and ones in the north can require significant energy for heating. The so called “green” building movement has an interest in the design of buildings which conserve energy required to maintain at a temperature comfortable for human occupation to reduce overall energy demand. With improved energy efficiency, the amount of oil, gas, electrical energy or other energy required to heat and cool such a building can be reduced, thereby reducing the CO2 production and the environmental footprint, as well as the costs of operating the dwelling to the owner.
In general buildings are subject to three types of temperature cycles, all having a different time period. The first cycle is the daily cycle which typically involves increasing temperatures during the day, and decreasing temperatures during the night. For example in Kingston, Ontario the daily cycle is about plus or minus four degrees Celsius on average, although the actual daily extremes can be much larger than the average. The next cycle is a local weather cycle which may last a period of days as warm fronts or cold fronts move through changing the temperature somewhat in the space of a few days. Again, in Kingston the average weekly variation is typically between 20 to 25 degrees Celsius, although again it can be much more or less than that in an extreme case. The longest period temperature changes are imposed by the seasons, which include the transition from the warmth of summer to the cold of winter. Of course to some extent these temperature variations are dependent upon the geographic location of the building, with colder average temperatures, in the northern hemisphere being found the further north the building is located.
Insulation to restrict heat loss, or heat gain, for example, through a building wall or roof is a commonly used building technique at the present. Generally the more the insulation the slower the rate of any heat loss through a wall or the like and the less energy is required to heat or cool the interior of the building to maintain it at a temperature that is comfortable for human habitation. However, even with large amounts of insulation additional energy is still required to make up for heat losses and gains that occur through the walls or other exterior surfaces. In some cases a high mass wall module is provided to act as a thermal energy flywheel for daily temperature fluctuations such as disclosed in U.S. Pat. No. 4,263,765. However such a design does not address the weekly and annual temperature cycles to any extent.
A building structure is subject to certain natural energy which impinges on it. For example, sun and wind energy are available to a greater or lesser extent for all buildings. Attempts have been made in the past to use such naturally occurring energy to help supplement the energy requirements of for example a house, through the use of small windmills or solar panel arrays. However such systems have limitations in the amount of energy they can usefully provide to a conventional building design, in part because there is a mismatch between when the energy is needed (say at night when the outside temperature cools down) and when it can be harvested (during the day when the sun is shining). As well, the amount of energy that is available to be harvested is can be far less than what is required to maintain a desirable temperature within the building in certain seasons. Further such systems can be costly and the cost of such a system can outweigh the energy savings that might otherwise be obtained. As well such systems can be perceived as being technically complex and thus not desirable for the average home owner.
Some prior designs have tried to harvest the energy impinging upon a building structure by incorporated liquid filled tubes located on the exterior surfaces of the outside walls, for example, to absorb the passive solar energy or heat that a building structure may be exposed to. Examples of such systems include the inventions disclosed in the following U.S. Pat. Nos. 4,274,396; 7,077,124; 3,893,506; 4,508,102; 6,079,179 and 6,220,339. In particular, in U.S. Pat. No. 6,220,339, the energy harvested from the outer surface of the exterior walls by means of tubes which act as a heat exchanger. The heat harvested in this way is taken to a heat sink in a basement for example, to be stored for later use. The heat sink may be in the form of a gravel mass, located under the building. After sun set for example the energy can then be recovered from the heat sink and reused to warm the building. To improve efficiency the patent teaches that the heat sink can be divided into a series of zones or regions of different temperatures to limit heat losses. However, this prior patent teaches essentially a passive solar collector to take energy from the outside of the building and to temporarily store it on the inside of the building, without addressing the dynamic of heat loss through the building walls themselves.
What is desired is an efficient building system in which passive or other harvested energy can be used to better control the inside temperature of a dwelling intended for human occupation. Ideally such design and system will permit an efficient temperature control which can respond to daily, weekly and even seasonal variations and will be easy to use and cost effective to install. Further such a system will be able to usefully use even small amounts of energy such as can be harvested or recovered from heat recovery systems, that might otherwise be wasted. Lastly such a system can address the dynamic of the heat loss through a surface in an active way to limit the energy required to be supplied inside of the building.